Understanding Magnetism, Electricity, and Light: A Comprehensive Overview

Classified in Physics

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Permanent Magnet

: once magnetized, remains magnetized. Ferromagnet: easily magnetized (iron, nickel, cobalt, some rare-earth metals, magnetite). Paramagnet: magnetized with more difficulty. Diamagnet: repels magnetic fields (slightly) - “not magnetic”./Materials can be broken into smaller chunks, called “domains”. Each domain has a miniature magnetic field. Materials may look the same, but at a smaller level, domains could be different - hence why some are magnets (or magnetize easily) and some don’t. Material, Temperature, Condition, Size & Shape*, Distance, affects magnet strength. All magnets* have two poles; North and South. At poles magnet is at its strongest (repelling or attracting). Breaking a magnet turns into 2 smaller magnets.

Magnetic Fields

: the force of magnets can be felt over a distance.To help visualize the force, scientists draw field lines. Draw arrows from N to S. lines close together=stronger forces. Compasses used to “see” the magnetic field lines. The Earth has a magnetic field-like a bar magnet buried within. True North ≠ Magnetic North<-moves. (difference is “declination”).

Magnetic Systems

contain energy! Specifics depends on what magnets (objects) are in the system: Opposite poles naturally attract. Close together is a low-energy state. It takes an outside force to pull the magnets apart. When you apply a force, you are increasing energy. Like poles have low energy far apart.

Static Energy:

Atoms are building blocks of universe. All atoms are made of some combination of neutrons, protons, and electrons. Protons do not typically move from one atom to another (too large). Instead electrons move from one object to another when energy is added to the system (usu. through friction).Charges can be positive (protons) or negative (electrons). May also be neutral (to start). Neutral does NOT mean no charge, but that the + and - charges ADD to 0. Objects can be charged by Conduction, Induction, Friction. Electroscope: device used to qualitatively demonstrate the effect of charged objects. Electric Force:similar to magnets, depends on size of charge and distance. Coulomb’s Law (Electric Force). Also similar to gravity (it too depends on size/mass of object and distance). Universal Law of Gravitation (Gravitational Force). Like the magnetic field, electric force can act over a distance. Electric Field lines help visualize the force. INTO - charges and OUT OF + charges, Shaped like spokes on a wheel. More field lines = stronger charge. Draw 2D but they’re 3D. The concepts of force, work, and energy are present with electricity (and magnetism). Energy can be increased in a system when you do work on objects.

Electricity → Magnetism

. At a small (quantum) level: Electric Field = Magnetic Field (perpendicular). Moving electrons in a wire is known as current; current creates a magnetic field. More coils or more current results in a bigger magnetic field.

Magnetism → Electricity.

Since magnets and electrons have magnetic fields, they affect each other. Magnet needs to be moving to cause a current in a wire. Increase current by using a big magnet or moving magnet quickly. This can also cause small changes in the electrons in other materials (non-wires). Generator: Mechanical Motion → Electricity. Motor: Electricity → Mechanical Motion! Waves=disturbance that carries energy. Mechanical wave.


(compression) waves are sound waves, sometimes drawn as transverse waves. Wave transfer ENERGY;not particles. Larger waves=more energy. Sound can’t travel in space b/c no medium. Fastest in solids (more particles), slowest in gases. Sound is just vibrating particles. Our ear is able to feel the vibrations and interpret them as sounds (at certain frequencies of 20-20000hz) Above is ultrasound. Infrasound below. Ear is funnel shaped to direct sound. Bigger amplitude=more energy=louder.

Loudness Measured in

watts/meter2 AKA dB. Hotter air, faster moving particles, faster sound travels.

Doppler effect

=frequency shift due to movement of an observer or source of sound. *tells nothing about loudness*.

Sonic Boom

=traveling faster than speed of sound. Freq=waves/sec. period =secs/wave. Interference-2 or more sound waves in same medium will interfere. Beats-when interfering  waves have diff freq (wah wah). Standing waves-sound waves interfere in perfect constructive/destructive way. Perfect D there is a node (no motion). Perfect C is antinode (max motion. Chladni Plates-Higher freq=more complex image.Resonance-standing wave is aka harmonic, based off of the fundamental frequency. Increased amplitude whens two waves construc interfere. In musical instruments. Acoustic Levitation: Two speakers face eachother and create a standing wave, at certain points there are nodes you can make water levitate cuz no vibration. v=f(double pipelength for wavelength in open). v=331+.6T(Ignore hz). Gauss gun:Steel ball attracts when flicked, speeds up, energy transferred. Iron in our blood is diamagnetic, and very little iron in blood. Friction by rubbing together + -. Conduction 0 + touch. Induction no touch. Electric force inverse, bigger distance smaller force.Tesla coil: switch turns on and off fast creating mag field b/c of changing current.passing thru coils from EM induction.Maglev: perm magnets are to repel or attract to electromagnets on track. Electromagnet is wire wrapped around nail. Motor is spinning wire !Light is a particle:  Energy of Light is contained in small packets. bundles of energy=photons. Explains why light can travel through space. explains “Photoelectric Effect”>Energy from the light shining on a metal plate gives electrons in the metal enough energy escape. Bright light has more energy than dim light, but dim blue light can dislodge electrons while bright red light cannot. Low fre. light (red/orange) cannot eject electrons. High freq. light (blue/viol.) can eject electrons./Instead of light as individual particles, we think as rays. Shows detection of light. Rays (arrows) show the straight-line nature of light/ Waves come in mechanical&electromagnetic, can be longitudinal(particle and wave are parallel) or traverse(particle&wave are perpendicular)/Light is a Wave, behaves like waves! transverse, electromagnetic wave. Light reflects, diffracts, and refracts.//Wave - Particle Duality,light is a wave AND a particle, light sometimes behaves like particles and sometimes like waves.//*EM Spectrum? Particles (electrons, photons, etc.) create changing E and B fields as they move. we can see EM waves!/warmer=more energy, colder=less energy./Light Moving,..Velocity or Speed can change depending on the situation. Speed of light is a fundamental constant. the speed of light depends upon the medium through which it travels. c = 3 x 108 m/s (300,000,000 m/s) ~ This can be substituted for v: c = d/t , c = f???? //Energy? A constant speed means as frequency increases, wavelength decreases. c = λ????, tied in to energy?: E = h???? , h = Planck’s Constant (6.626 x 10-34 Js)//Low Energy-Radio Waves (Microwaves) so small energy usually not reported./ Electron Volt (eV) 1 eV = 1.60218 x 10-19 j/Even with new unit, low energy lights contain smaller than 1 meV (10-3 eV)//Medium Energy=(Microwaves) Infrared, Visible (Ultraviolet), 0.001 eV to 10 eV (1.6 x 10-22 j to 1.6 x 10-18 j)// High Energy=(Ultraviolet) X-Rays and Gamma Rays Energies greater than 10 eV. AKA  ionizing radiation; enough energy to rip electrons from atoms and molecules!//Effect of Mediums-Much like sound waves change in different mediums, so to does light! LIGHT travels fastest thru vacuum,//light travels slowest in diamond because the amount of refraction//Superposition of Light=Multiple waves interact with each other in superposition. Two waves in same space will add together. Above equilibrium (crest) = positive. In reflection, diffraction, and refraction; it is the combination (superposition) of waves that results in what we see.//Resolving Light:Light coming from two sources will interact.// Reflection: Waves hit a boundary and bounce back.//Bubbles:multiple reflections interfering w each other(superposition)//Diffraction=waves hit a corner of a boundary&bend around(Young’s slit exp.), diffraction gratings produces rainbows->wavelength dependent! Longer wavelength, more it bends (diffracts).// Polarization-related to diffraction, only works bc of perpendicular nature of the electric magnetic fields of light. Pglasses=vertical.//Refraction:waves hit new medium&speed up or slow down. Light has bigger angle for faster.//Speed of Light: c = 3 x 108 m/s. Issa constant; it is also for light in a vacuum.//Mirages:waves can refract. Air behaves diff in diff air. Light travels faster in cold air. Inferior mirage=below what it should be, superior=above&reflected// Dispersion: refraction also wavelength dependent. Blue light refracts more than red light bc of WVL.. blue bends @ greater angle.// Rainbows: enters raindrops&refreacts back into our eyes at certain angle. Each particle reflects a diff light, mass raindrops=rainbow.//Fiber optic cable: waves can refract&reflect:Light follows liquid through bucket bc of total internal reflection. Light reflected asa hitting interface of air and liq. bc light goes through diff med at diff freq.//Shorter wvl, higher freq./longit=back and forth/elec spec travel same speed © but diff freq.)/violet has highest energy lvl/light ^ wvl V/evl ^, energy V/Transparant:pass completely. Translucent:partly pass.//Luminous-own souce, illuminous-reflects/black absorbs all color, white reflects all colors, blue reflects blue/lens have limited resolution/dispersion/rough=diffuse reflection/perpendicular to block/ Both send radio waves (invisible light) to cell towers. We use digital more cause short bursts are easier.

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